For protection against dazzling of the driver or other occupants, conventional motor vehicles have mechanical sun visors. These are hinge-mounted on the vehicle roof and can be pivoted downward as needed to prevent or at least to mitigate the dazzling of the driver or front-seat passenger, for example, when the sun is low.
Also known, are windshields into which a sun visor is integrated in the form of a functional element with electrically controllable optical properties, in particular with electrically controllable transmittance or scattering properties. Thus, the driver can control the transmittance behavior of the windshield itself relative to sunlight; the conventional mechanical sun visor can be dispensed with. By this means, the weight of the vehicle can be reduced and space is gained in the roof region. In addition, electrical control of the sun visor is more convenient for the driver than the manual folding down of the mechanical sun visor.
Windshields with electrically controllable sun visors are, for example, known from DE 102013001334 A1, DE 102005049081 B3, DE 102005007427 A1, and DE 102007027296 A1.
One possible controllable functional element for realizing the controllable sun visor is a so-called “PDLC” functional element (polymer dispersed liquid crystal). The active layer contains liquid crystals that are incorporated into a polymer matrix. When no voltage is applied, the liquid crystals are randomly oriented, resulting in strong scattering of the light passing through the active layer. When a voltage is applied to the flat electrodes, the liquid crystals align themselves in a common direction and the transmittance of light through the active layer is increased. The PDLC functional element acts less by reducing total transmittance, but rather by increasing scattering to ensure protection against dazzling.
PDLC functional elements have, in the voltage-free state, a white, milky appearance, which is frequently considered unaesthetic. Consequently, such controllable sun visors are poorly accepted by the auto industry and the end user.
U.S. Pat. No. 4,749,261 A discloses a vehicle composite pane with an electrically controllable functional element laminated therein, which can have a tinted or colored flat electrode. The functional element can be obscured thereby; however, strict limits are imposed on the design freedom since the tinting is restricted to the actual functional element.
US 2014/192286 A1 discloses a composite pane with an electrically controllable functional element laminated therein. The thermoplastic intermediate layers via which the functional element is bonded to the glass panes can be completely tinted or colored.
US 2015/331296 A1 discloses a composite pane with an electrically controllable functional element laminated therein, wherein the glass panes can be completely tinted or colored.